What Causes A Hard Dark Growth Near The Toe Cuticle Post Injury?

Hi, I stubbed my toe (the second to last toes on the left foot) a couple of weeks ago against a wall, It hurt for a couple of hours but after that the pain subsided. However I have now noticed that there is a black, hard substance near the cuticle. There is no pain or puss or any other usual signs of infection. What do you think this is?